The present invention relates to a prosthesis, and more particularly, to a fastener for a prosthesis that stably holds a prosthesis on a residual limb.
A prosthesis is used to replace a missing extremity. For example, a prosthetic leg is attached to a residual leg, and a prosthetic arm is attached to a residual arm. There are a wide variety of such prostheses.
FIG. 3 illustrates an example of a typical prosthesis 1 attachable to a residual limb S, which is a leg in this case. The prosthesis 1 includes a liner 2, which is worn on a residual limb S, and a socket 3, which is fitted onto the residual limb S with the liner 2 arranged in between. The liner 2 is formed from a suitable material such as synthetic leather and shaped in conformance with the residual limb S. The socket 3, which includes a hollow portion 3a, is formed from a suitable material such as a fiber reinforced resin and shaped in conformance with the residual limb S. The hollow portion 3a receives the residual limb S with the liner 2 worn thereon.
When using the prosthesis 1, the liner 2 may slip out of the hollow portion 3a of the socket 3 or fall off from the residual limb S. In the prior art, therefore, a fastener such as a belt 4 is arranged on the socket 3 and fastened to a portion above the residual limb S (in this example, the knee). This prevents separation of the prosthesis 1 from the residual limb S.
As described above, in addition to the liner 2 and socket 3, the prosthesis 1 of the prior art requires a discrete fastener such as the belt 4 to prevent separation of the prosthesis 1 from the residual limb S. This makes the structure of the prosthesis 1 complicated. Further, a fastener such as the belt 4 may interfere with movement of the user.
A liner may be secured to a socket by using a fastener including a first fastening piece, which is arranged on a distal end of a liner, and a second fastening piece, which is arranged at the bottom end of the hollow portion of a socket. The first and second fastening pieces are fastened together to secure the distal end of the liner to the bottom end of the hollow portion in the socket. In this case, however, the internal structure of the prosthesis would also be complicated. Further, space for the fastener is necessary at the bottom part of the hollow portion in the socket. However, since the length of the residual limb differs between each person, sufficient space for this fastener may not be available in the hollow portion. For this reason, the versatility of such a structure is low. Additionally, burdensome fastening and unfastening tasks would become necessary when using such a fastener. Moreover, such a fastener pulls the liner toward the bottom end of the hollow portion in the socket. This, in turn, may pull the residual limb and be uncomfortable for the user. If the residual limb is constantly pulled in such a manner, this would result in the flesh at the residual limb being stretched.
One type of a liner is formed from a flexible material such as silicon resin. This liner adheres to the residual limb and the wall of the hollow portion in the socket so that the prosthesis is not separated from the residual limb. By using such a liner, a discrete fastener does not have to be used to prevent separation of the prosthesis from the residual limb. However, this liner adheres to the residual limb. Therefore, the liner may become moist or irritate the residual limb. This is uncomfortable for the user. Further, the residual limb seals the interior of the liner. This may produce unpleasant noise when movements of the user cause air to leak out of the liner. This is also uncomfortable for the user.